This invention relates to dental laboratory equipment and particularly to a novel and improved mounting ring for securing plaster models of dental arches to a dental articulator.
A dental articulator is a well-known dental laboratory tool for adjustably supporting dental casts in a position corresponding to the actual position of the jaws for which dentures are to be made, and includes adjustment provisions by which upper and lower jaws may be moved relative to each other as necessary to accurately depict the occlusal planes of the patient's original teeth. Generally, an articulator includes a stationary base plate for mounting a plaster cast that supports the patient's lower dental arch, and an adjustable and calibrated overlying bow member to which is mounted a plaster cast supporting the upper dental arch.
The arch-supporting plaster casts must be rigidly attached to the base or bow member of the articulator in order to prevent the construction of an improperly formed denture. The plaster casts are, therefore, molded with an internal mounting ring containing a threaded female member adapted to engage the threads of attachment screws extending through the base or bow members of the articulator. In addition, a keyway in the mounting ring is adapted to engage an alignment pin in the base or bow members to prevent possible rotation of the plaster cast around the axis of the screws. Thus, the plaster casts are assembled by pouring the plaster in its liquid state into a mold formed around the mounting ring.
Mounting rings for all types of articulators are readily available in either metal or plastic, both of which provide a good mechanical bond to the attached plaster cast. At the current price range, the typical cost of a ring is between one-half to two dollars per mounting ring. The mounting ring of the present invention may be very rapidly made by the dental laboratory technician at a current material cost of approximately 5 cents per mounting ring and provides not only an effective mechanical bond to an attached arch-supporting plaster cast, but also provides a molecular bond to the cast, thereby resulting in a solid unitary module.
Briefly described, the mounting ring of the invention is constructed of a strong dental stone or other suitable dental plaster which, in its liquid state, is poured into a resilient mold having a cylindrical wall section and a floor section that contains islands for producing the desired internal shape of the mounting ring. A vertical post located on the floor of the mold supports a threaded nut which becomes cast within the plaster mounting ring to be used to attach the mounting ring to the base or bow members of an articulator. After the nut has been placed on the post and the liquid plaster poured, a piston is forced down by hand pressure into the mold to a point where it is stopped by the top surface of the islands, thus removing air pockets in the casting and forcing out the surplus liquid plaster between the sides of the piston and the resilient wall of the mold. When the plaster has hardened, the resiliency of the mold permits easy removal of the completed mounting ring.